I go to a ranked "primary care" medical school. My letters were not from "big wigs"... in fact, while I hold tremendous respect for everyone who wrote me letters (and would argue that they ARE some of the best), none of them have much more than regional name recognition... no major research backgrounds, no national positions in academies/societies, no procedures/implants named after them, etc.
In fact, you bring up a good point... having relied almost entirely on this biased forum, I was convinced entering this interview season (pre-Step 2 score) that I was on the losing end of average (based on the Match Statistics document), and would struggle for my 10 interviews... I thought 220 was going to hurt me with "cutoffs". I don't think it has.
Anyway, my point is that if you are sub-230 entering fourth year, you can work your butt off on SubI's, keep a smile on your face, get strong letters, and set aside time for Step 2, and suddenly a below mean application becomes a strong one.
As an aside, there are no guarantees... I know of a few guys with stronger initial stats than mine that, were I a chairman, I would have loved to have in my program, yet they haven't been quite as lucky... who knows...